Men in our culture are taught to not cross their legs at the knee. Instead, our social norms require that men are only supposed to sit is with their legs open and feet flat on the floor, or with the ankle resting on the opposite knee so as not to appear effeminate.

Crossing one’s legs is considered an effeminate habit. In his book "Gay Histories and Cultures: An Encyclopedia", George E. Haggerty tells that a comprehensive survey of effeminacy published in 1975 in The Archives of Sexual Behavior presents 67 questions devised by four behavioral scientists. One of them is, “When he sits, does he double-cross his legs, that is, at both knees and ankles?” The gay men surveyed “displayed a much greater tendency toward effeminacy than their heterosexual counterparts,” Haggerty writes.

But new studies have found that there actually may be health reasons why sitting this way is preferable for everyone regardless of gender.

Here are the top 9 health risks of crossing your legs at the knee, based on medical research:

1) Crossing Your Legs Raises Your blood pressure - Did you know that crossing your legs at the knees increases your blood pressure?According to a 2007 study conducted by Radboud University in Nijmegen, the Netherlands found that crossing your legs at the knee caused spikes in your blood pressure. Crossing your legs at the ankles did not cause an increase in blood pressure.

How much does crossing your legs raise blood pressure? The study from the Netherlands examined 111 patients, 60 women and 51 men. 49 people in the group had high blood pressure and 28 were diabetics. The study found that crossing the legs at the knee increased systolic (top number) blood pressure by 6.7 points among those with high blood pressure and increased diastolic (bottom number) blood pressure by 2.3 points among those who had diabetes. Among those with diabetes, crossing their legs at the knees raise systolic blood pressure (top number) by 7.9 points and raised diastolic blood pressure by 1.7 points.

A 1999 study by the University of Calgary’ Faculty of Medicine in Alberta, Canada, determined that not only does blood pressure increase when legs are crossed, but also that this increases many patients’ cardiovascular risk.

The researchers recommended that patients place their feet flat on the floor when having their blood pressure measured so as to get an accurate reading. This last finding was corroborated by a study done by Turkey’s Ege University School of Nursing that published in the Journal of Clinical Nursing in 2006. These researchers said that blood pressure measurement must be taken in with patients in the sitting position with their arms supported at the right a trial level to prevent statistically important changes in systolic blood pressure.

More specifically, a 2009 study by Sheffield University in the U.K. on hypertensive patients found that blood pressure rose significantly with the crossed leg position: systolic and diastolic blood pressure escalated approximately 10 and 8 mmHg, respectively.

2) Crossing Your Legs Can Increase scrotal temperature – A study published in 2007 found that fertile men seated with their legs crossed, whether naked or clothed, experienced a persistent effect on scrotal temperature, which could have both patho-physiological and epidemiological implications, according to the Human Fertility Research Group, Université Toulouse III in France.

3) Sensory disturbance – It’s been found that a history of prolonged sensory disturbance or weakness lasting hours or days will follow relatively trivial pressure on an exposed nerve, which can be caused by sitting with crossed legs for several hours, as this causes pressure on the common peroneal nerve at the head of the fibula. The study, “Assessment and diagnosis of sensory disturbance,” was published last year in the Oxford Journal InnovAiT.

4) Varicose veins – Long periods of time spent sitting with one’s legs crossed at the knee can cause the formation of varicose veins and can also exacerbate an existing condition by inhibiting blood circulation, informs John D. Kirschmann’s 2006 book Nutrition Almanac.

5) Deep vein thrombosis (DVT) - Sitting with crossed legs can injure the endothelium of the veins in the legs, which can act as a precursor to DVT, the formation of a blood clot in a deep vein and which can in turn cause a pulmonary embolism, according to a study by K.R. Aryal and H. Al-khaffaf published in the European Journal of Vascular and Endovascular Surgery in 2006.

6) Crossing Your Legs Can Cause Back pain – “By crossing your legs, you're overstretching one side of the body and not the other, which will affect the pelvis and then the spine,” explains chiropractor Attracta Farrell, a chiropractor based in Ireland.

7) Thigh pain via entrapment syndrome of the lateral femoral cutaneous nerve - This common entrapment syndrome entails pain felt over the upper anterolateral thigh area. It takes place at the anterior superior iliac spine, as the nerve passes through the inguinal ligament. The pain is caused by prolonged sitting with the legs crossed, among other phenomena, according to Dr D Gotlieb, whose article appeared in Rheumatology News (South Africa).

8) A deformed pelvic ring –Crossing one’s legs produces an inward deformation of the pelvic ring, according to a 2006 study by the Department of Biomedical Physics and Technology at the University Medical Center Rotterdam in the Netherlands. Cross-legged sitting produced a relative elongation of the piriformis muscle of 11.7% versus normal sitting. “Application of piriformis muscle force resulted in inward deformation of the pelvic ring and compression of the sacroiliac joints and the dorsal side of the pubic symphysis,” the researchers wrote.

9) Peroneal neuropathy – sitting for a prolonged period of time with one’s legs crossed can spark peroneal neuropathy, according to Neurology in clinical practice, Volume 1 by Walter George Bradley. This is a nerve condition that entails functional disturbances and pathological changes in the nerves, such that the victim can experience loss of sensation or paralysis. The peroneal nerve starts at the sciatic nerve and enables the transfer of nervous energy and stimulation to the calf and foot.